1. Field of the Invention
This invention relates to a carbon black graft polymer. More particularly, this invention relates to a carbon black graft polymer having a high carbon content and exhibiting improved dispersibility to various substances such as water, organic solvents, and organic high polymers.
This invention further relates to a static charge developing toner using the carbon black graft polymer mentioned above and other products containing the carbon black graft polymer.
2. Description of the Related Art
Since the carbon black excels in coloring property, electroconductivity, weatherability, chemical resistance etc., it is extensively utilized in various applications such as a reinforcing agent and a filler for plastics and elastomers. The carbon black, however, is rarely used by itself because it has the form of powder or grains. Generally, it is enabled to manifest the characteristic properties thereof by being uniformly dispersed in such solid basic materials as rubber or resin or in such liquid media as water or solvents. The carbon black, however, is uniformly mixed or dispersed with extreme difficulty under ordinary mixing or dispersing conditions because it has weak affinity for other substances such as, for example, organic macromolecular compounds, water, and organic solvents as compared with the cohesive force manifested between particles.
For the purpose of solving this problem, numerous studies are being pursued with a view to improving the dispersibility of hydrophilic particulates by coating the surface of the hydrophobic particulates with a varying surfactant or resin thereby causing the hydrophobic particulates to acquire exalted affinity for a medium wished to form a dispersion.
For example, (1) the carbon black graft polymer which is obtained by polymerizing a polymerizable monomer in the presence of carbon black has been attracting attention because it is enabled to have hydrophilicity and/or lipophylicity suitably varied by suitably selecting the kind of polymerizing monomer (JP-B-42-22,047, JP-B-44-3,826, JP-B-45-17,248, U.S. Pat. No. 3,557,040 etc.). Then, (2) the carbon black graft polymer obtained by the reaction of a polymer possessing such a reactive group as epoxy group or aziridine group in the molecule thereof with carbon black has been proposed (JP-B-02-24,868, JP-B-06-27,269 etc.). Further, (3) the carbon black graft polymer obtained by radically trapping in carbon black a polymer radical formed by the thermal decomposition of a polymer containing an azo bond or a peroxide bond in the molecule thereof in the presence of carbon black or the carbon black graft polymer obtained by subjecting a polymeric peroxide compound of a specific structure to partial thermal decomposition in the presence of carbon black thereby introducing a peroxide group in the carbon black and then decomposing the peroxide group on the surface of carbon black in the presence of a vinyl monomer thereby grafting a vinyl polymer to the surface of carbon black has been proposed (JP-A-06-263,830).
Indeed, the use of these carbon black polymers exalts the dispersibility of carbon black in resin or other matrix and improves the properties of the matrix. Even in the use of such carbon black graft polymers, when the amount of carbon black incorporated in the matrix is increased, for example, to a level exceeding 10 wt. % based on the total weight of the composition incorporating the carbon black, the end product formed of this composition fails to impart sufficient dispersibility to carbon black and suffers properties thereof such as coloring property, electric resistance, dielectric property, and amount of electrification to disperse.
An object of this invention, therefore, is to provide a novel carbon black graft polymer.
An another object of this invention is to provide a carbon black graft polymer having a high carbon content and excelling in dispersibility.
Still another object of this invention is to provide a novel static charge developing toner.
Yet another object of this invention is to provide a static charge developing toner capable of producing a fixed image of satisfactorily high photographic density and high resolution at a low application rate.
The objects mentioned above are accomplished by a carbon black graft polymer comprising a carbon black and a polymer chain grafted thereto, which is characterized by that the carbon black has a specific surface area of not more than 120 m2/g.
This invention also discloses the carbon black graft polymer which is characterized by being obtained by subjecting 100 parts by weight of carbon black having a specific surface area of not more than 120 m2/g and an oil absorption, regarding dibutyl phthalate, of not more than 70 ml/100 g and 5-100 parts by weight of a polymer having a reactive group exhibiting reactivity to the functional group on the surface of the carbon black to a thermal reaction.
This invention further discloses the carbon black graft polymer produced by the thermal treatment mentioned above which is carried out by melting the polymer mentioned above and kneading it with the carbon black mentioned above.
This invention further discloses the carbon black graft polymer produced by the thermal treatment mentioned above which is carried out by heating and stirring the carbon black mentioned above and the polymer mentioned above in the presence of a liquid dispersing medium.
This invention further discloses the carbon black graft polymer characterized by being obtained by heating and stirring 100 parts by weight of carbon black having a specific surface area of not more than 120 m2/g with 5-100 parts by weight of a block or graft type polymer formed of a segment (A) containing a reactive group having reactivity with the functional group on the surface of the carbon black and an anther segment (B) differing in structure from the segment (A) mentioned above in the presence of a liquid dispersing medium.
This invention further discloses a hyperdispersoid of carbon black characterized by being dispersed in a matrix selected from the group consisting of resin, rubber, and solvent a carbon black graft polymer comprising a carbon black having a specific surface area of not more than 120 m2/g and a polymer chain grafted thereto.
This invention further discloses a static charge developing toner characterized by containing a carbon black graft polymer comprising a carbon black having a specific surface area of not more than 120 m2/g and a polymer chain grafted thereto.
In the static charge developing toner according to this invention, the carbon black content mentioned above is preferred to be in the range of 12-35 wt. % based on the total weight of the toner.
The carbon black graft polymer according to this invention exhibits fine dispersibility in target media such as varying resins, rubbers, and solutions despite the relative small weight of the grafted polymer component to the weight of the carbon clack component, namely the high carbon black content thereof. The use of the carbon black graft polymer according to this invention, therefore, enables carbon black to be distributed with fine dispersibility at a high concentration in a varying composition or blend and enables the ability of the composition or blend to acquire electric resistance property, charging property, mechanical strength etc. to be adjusted as expected.
Further, the static charge developing toner according to this invention acquires fine dispersibility of carbon black even when the carbon black content thereof is increased, for example, to such a high level as exceeding 15 wt. % and excels in such toner properties as electric resistance and charging property. Since the toner is enabled to manifest the properties as required despite the increase of the carbon content thereof, the produced fixed image acquires a fully satisfactory photographic density even when the toner is used only at a low application rate. The toner permits a reduction in the consumption thereof and allows compaction of the equipment.
The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments.